Many common types of computer numerical control (“CNC”) machine tools can generally be described as rigid hard cutting tools. These traditional machine tools employ hard tooling, generally metal, which spins rapidly about one or more spindles to sculpt or chip away at a target workpiece, while moving forward along a target tool path, generally at a set speed, all as designated by a computer aided manufacturing (CAM) program and the operating parameters of the machine tool employed. Multiple tooling passes typically occur along the same tool path geometry, so that the workpiece gradually takes the intended or target shape, from the chiseling that occurs with each successive sculpting pass of the spinning rigid hard tooling. Other than dulling/losing consistent sharpness, the rigid hard tooling maintains its original shape throughout the machining process.
A separate class of CNC cutting tools that do not employ rigid hard tooling are referred to as beam cutters. In such beam cutters, a beam, employing plasma, waterjet, torch (such as oxyacetylene), or laser, as examples, and operating along a defined tool path, either erodes (waterjet or abrasive-jet) or melts (laser, plasma, or torch) a workpiece, in some cases through the entire thickness of the workpiece. Etching, engraving, blind hole or pocket milling strategies may also be employed.
For beam cutter machine tools, the cutting head is generally never in actual physical contact with the workpiece, but rather hovering just near the workpiece, with the cutting beam directed against the workpiece surface. Beam cutter machine tools exhibit unique cutting characteristics, in that the cutting beam itself is not rigid (differing from hard rigid tooling) and may exhibit multiple changes in shape along a given tool path, as influenced by, among various factors, the energy of the beam cutter itself; the geometry; thickness and target workpiece material.
Waterjet cutting systems and other fluid cutting systems are examples of beam cutter machine tools. Waterjet cutting systems, such as abrasive-jet cutting systems, are used in precision cutting, piercing, shaping, carving, reaming, etching, milling, eroding and other material-processing applications. During operation, waterjet cutting systems typically direct a high-velocity jet of fluid (e.g., water) toward a workpiece to rapidly erode portions of the workpiece. Depending upon the resistance to the cutting process of a particular target workpiece material, abrasive material can be added to the fluid to enable and/or to increase the rate of erosion. When compared to other material-processing systems (e.g., grinding systems, plasma-cutting systems, etc.) waterjet cutting systems can have significant advantages. For example, waterjet cutting systems often produce relatively fine and clean cuts, typically without heat-affected zones around the cuts. Waterjet cutting systems also tend to be highly versatile with respect to the material type of the workpiece. The range of materials that can be processed using waterjet cutting systems includes very soft materials (e.g., rubber, foam, balsa wood, and paper) as well as very hard materials (e.g., stone, ceramic, and metal). Furthermore, in many cases, waterjet cutting systems are capable of executing demanding material-processing operations while generating little or no dust, smoke, and/or other potentially toxic byproducts.
In order to perform a cutting project using a waterjet cutting system, it is typical to provide a stream of machine commands and related control signals (hereafter simply “machine commands”) to the waterjet cutting system. These include turning the jet on, turning the jet off, moving the source of the jet in two-dimensional or three-dimensional space in a particular direction and speed, and rotating the source of the jet or the workpiece or both in one or more dimensions relative to its movement. A variety of approaches are used to generate such a stream of machine commands that will cause a waterjet cutter to process a workpiece in a manner consistent with a cutting design specifying the size, quality, and shape of elements of the post-processed workpiece.
In a similar manner, beam cutter machine tools of other types are also controlled by providing stream of machine commands, including turning the beam on, turning the beam off, moving the source of the beam in two-dimensional or three-dimensional space in a particular direction and speed, rotating the source of the beam or the workpiece in one or more dimensions relative to its movement, modulating the energy, diameter, flow rate, cross-sectional shape, and/or other attributes of the beam.